Heat exchange units



Oct. 20, 1964 R. W. KRITZER HEAT EXCHANGE UNITS INVENTOR. RlCHARD w.

KRITZER A-r-rY 3 SheetsSheet 1 6 M Z Z 2 P h I04 BY Criginal Filed Feb. 4, 1960 1964 R. w. KRITZER 3,153,443

HEAT EXCHANGE UNITS Original Filed Feb. 4, 1960 3 Sheets-Sheet 2 ,80 i2. EQ I4- /00 5 2 INVENTOR.

. I I l V V 4% 4o |4 42 Rncumzo W. Km ZER ATTY.

Oct. 20, 1964 w. KRITZER 3,153,443

HEAT EXCHANGE UNITS Original Filed Feb. 4, 1960 3 Sheets-Sheet 3 2224 E25 zzz ZIZ INVENTOR. Emu-A20 W. Ken-zen aligned open-sided notches.

United States Patent 3,153,443 HEAT EXCHANGE UNITS Richard W. Kritzer, 1355 N. Astor St., Chicago 10, Ill. Continuation of abandoned application Ser. No. 6,782, Feb. 4, 1960. This application Dec. 3, 1962, Ser. No. 241,906

5 Claims. (Cl. 165-67) The present invention relates to heat exchange units and has particular reference to units of the type wherein serpentine lengths of tube stock having reach sections which are oval in cross section are pressed into notches of circular configuration provided in the edge regions of flat fin stock.

In my United States Patent No. 2,913,806, granted on November 24, 1959, and entitled Fabrication of Heat Transfer Units, there is disclosed a heat exchange unit of the same general type as that with which the present invention is concerned, together with an apparatus by means of which such heat exchange units may be formed. There is also disclosed in this patent a method which is involved in making the heat exchange units. The heat exchange units of the present invention are designed as improvements over the heat exchange unit shown in my prior patent above referred to in that they present functional advantages not present in the earlier unit, and also in that they may be manufactured at a much lower cost without sacrificing quality or efiiciency. Such lower cost of the present heat exchange units is made possible in that there is effected a very appreciable saving of the materials which cooperate to make up the heat exchange units, particularly a saving in the amount of fin stock required to produce a given number of fins from a given weight of fin stock material.

Briefly, and as exemplified in my prior patent mentioned t-hereafter, while confining such strips in suitable forming dies in their spaced relationship, progressively severing from the strips by a punching operation a series of disks of circular configuration slightly in excess of 180 so as to produce in the thus positioned strips plural rows of The various notches are in the form of major circle-sectors and each aligned row of such notches is adapted to receive therein with a tight fit the straight reach section of a length of serpentine tube stock. The serpentine tube stock is formed initially with straight reach sections which are oval in cross section so that these reach sections will fit loosely into the various rows of notches provided for them in the fin stock. After the reach sections have been thus loosely positioned in the rows of open-sided notches, a pressing platen is caused to force the reach sections against the bottom of the notches to expand the tubing to circular form and secure the same within the notches. The thus formed basic tubing unit stock may be assembled in various installations, utilizing suitable end plates or the like which are fastened to the tube stock near the serpentine bends and which constitute mounting means whereby the units as a whole may be secured in position in any given environment.

Reference may be had to my above-mentioned patent for a full understanding of the method involved in constructing such heat exchange units, and for a detailed description of the units themselves, however, for purposes of discussion herein, it is important to note that by the method outlined above the punching operations which are performed successively on the separate elongated 3,153,443 Patented Got. 20, 1964 ice rectangular consecutive strips of fin stock involves an actual removal of metal at the region where each notch is formed. Each notch is provided by the removal of a substantially D-shaped sing or disk of the metal, the disk having one fiat side representing a portion of the edge of the elongated strip of fin stock and an arcuate side representing the curved contour of the notch. Where small size fin stock is concerned, the percentage of scrap metal involved by the removal of such disks may amount to as much as 25%. With normal size fin stock, for example, in one standard size thereof involving fin stock which is one inch wide and employing notches which represent major circle sectors having a diameter of threeeights of an inch, the loss of metal is approximately 12%, not to mentioned the cost of cleaning-up operations and disposal of the discarded disks.

According to the present invention, instead of progressively punching notches in consecutively arranged elongated individual strips of flat fin stock, the strips are formed with the necessary tube-receiving notches already present therein by a shearing operation wherein the various identical strips are severed from -a large sheet of flat metal stock, utilizing the shearing action of a single pair of shearing dies which perform one shearing stroke for each strip of fin stock which is severed from the puzzle pieces having plural spaced tabs along one edge thereof and plural spaced notches along the other opposite edge thereof. In this manner, there is no loss of metal whatsoever involved in the process of forming the strips of fin stock, while in the finished heat exchange unit, the attached tabs on each strip of fin stock may be put to numerous advantageous uses as bracing, rigidifying, strengthening or reinforcing members, as desired, or as attachment means for the unit, while at the same time these tabs serve materially to increase the heat-radiating capacity of the unit as compared to conventional heat exchange units which are manufactured from the same quantity by Weight of the sheet metal stock.

The provision of a heat exchange unit of the character briefly outlined above being among the principal objects of the invention, numerous other objects and advantages of the invention, not at this time enumerated, will become more readily apparent as the nature of the invention is better understood.

In the accompanying three sheets of drawings forming a part of this specification, several embodiments of the invention have been shown.

In these drawings:

FIG. 1 is a rear elevatio-nal view of a heat exhange unit constructed in accordance with the principles of the present invention;

FIG. 2 is an end view, partly in section, of the structure shown in FIG. 1;

FIG. 3 is an opposite end view, partly in section, of the structure shown in FIG. 2;

FIG. 4 is a top plan view of the heat exchange unit;

FIG. 5 is a front elevational view of the unit;

FIG. 6 is an enlarged sectional view taken substantially along the line 6-6 of FIG. 1;

FIG. 7 is a two-part geometric diagram including subviews 7a and 7b and schematically representing certain surface area considerations association with the present invention;

FIG. 8 is a fragmentary plan view of preformed section of fin stock employed in connection with a modified form of the invention and showing the same operatively applied to a section of tube stock;

FIG. 9 is a fragmentary side elevational view of the medial region of a still further modified form of heat exchange unit;

FIG. 10 is a fragmentary side elevational view similar to FIG. 8 showing yet another modified form of heat exchange unit; and

FIG. 11 is a fragmentary perspective view, somewhat schematic in its representation, of a shearing die employed in connection with the formation of prefabricated fins from flat sheet fin stock, and illustrating its manner of use.

Referring now to the drawings in detail, and in particular to FIGS. 1 to 5, inclusive, wherein one form of heat exchange unit embodying the principles of the present invention has been shown and designated in its entirety at it). Briefly, the unit is comprised of a single length 12 of tubing which has been bent to serpentine form and to which there has been applied a series of closely spaced parallel elongated strips 14 of preformed fin stock, the fins extending across the straight reach portions of the serpentine tube stock. The assembled tube and fin structure constitutes a basic heat exchange assembly which may be operatively installed or mounted in a wide variety of installations by means of suitable supporting framework, as, for example, by specifically shaped end plates or mounting brackets 16 and 18, respectively, which fit over the reverse bends associated with the length of serpentine tubing 12. The end plates 16 and 18, in combination with the various formed stripsl i of fin stock, serve to rigidify the serpentine tubing and the latter similarly lends rigidity to the fin stock so that a compact and fairly rigid heat exchange unit or assembly results.

The method of attaching the strips 14 of fin stock to the serpentine length of tubing 12 is substantially the same as the method shown and described in my prior Patent No. 2,913,896, above referred to, and reference may be had to such patent for a detailed description of this method. It is deemed sufficient for purposes of disclosure herein to state that each strip 14 is severed, as shown in FIG. 11, from a large sheet or web 20 of flat sheet metal, preferably aluminum, and is so shaped as to provide one straight linear edge 22 which is interrupted at spaced regions therealong by arcuate notches 24 which constitute major circle sectors which are slightly greater in extent than 180. The length 12 of tubing includes a series of straight reach sections 26 (FIG. 1) connected together by reverse bends 23. The free ends 30 and 32, respectively, of the tubing length 12 terminate at the same end of the structure it), the end 3i) being coaxial with one of the reach sections 26 and the end 32 being turned laterally. Obviously, Where the serpentine tubing possesses an even number of reach sections 26, the ends thereof will terminate at the same end region of the structure it and where an odd number of such reach sections are provided, the ends 39 and 32 will terminate at opposite end regions of the structure.

As described in my above-mentioned patent, prior to its association with the fin structure, the straight reach sections of the tube stock from which the length 12 is formed are oval or elliptical in transverse cross section and the major axes of the ellipses are slightly less than the entrance opening of each notch 24. The various strips of preformed fin stock are suitably confined in slightly spaced parallel relationship with the various notches 24 arranged in straight rows. The straight reach sections 26 are placed or laid into the rows of notches and thereafter, by means of a suitable pressing platen, the reach sections are forced against the bottom of the notches and the oval reach sections are caused to expand into intimate contact with the edges of the notches 24 so as to fill the same as shown in FIG. 6 so that the fin strips 14 are frictionally bonded to the tubing length 12 in intimate heat exchange relationship.

As clearly shown in FIG. 11, each strip 14 of fin stock, in addition to its linear notched edge 22, has an opposite straight linear edge til-which is interrupted at spaced regions by the provision of a series of tabs or ears 42 which conform in size and configuration to the size and configuration of the various notches 24. The ears 42 are thus also in the form of major circle sectors and each ear is aligned transversely of the strip 14 with one of the notches 24. The end edges 44 and 46 of the strip 14 are preferably but not necessarily straight. The notches 24 and cars 42 are transversely aligned in pairs.

The method involved in forming the various strips 14 of fin stock from the flat metal sheet 20 is schematically illustrated in FIG. 11. This method involves a series of shearing operations which are performed successively upon the sheet 20 and entails no removal of metal what soever from the sheet other than the severance of the various strips 14 in their entirety. The method involved herein is to be distinguished from the method disclosed in my above-mentioned patent wherein individual fiat disks of metal are removed from the edge regions of the strips to produce the spaced notches in one side edge of each strip. Furthermore, by resorting to a shearing operation such as has been disclosed in FIG. 11, the use of costly confining and punching dies is eliminated.

Still referring to FIG. 11, the flat metal sheet 20 may be advanced periodically along a suitable table surface (not shown) and portions thereof successively brought into vertical register with upper and lower shearing dies 52 and 54, respectively. The upper die 52 may be a male die having a shearing edge 56 conforming in configuration to the configuration of the edge 22 which is formed on each strip 14, while the lower die 54 may be a female die having a shape conformable to the shape of the shearing edge 5%. Suitable means, not shown, which may be either manual or automatic, may be provided for causing vertical reciprocation of the upper die 52, as Well as for advancing the sheet 20 periodically along the table surface and between the dies 52 and 54. Each time the upper die 52 descends upon the lower die 54, one of the strips 14 is severed from the sheet 2 along the leading edge region thereof, the severance taking place without involving any waste or scrap material. After the severed strips 14 move past the dies in the direction of travel of the sheet 29, the various strips 14 will become stacked below the level of the table surface 56 as indicated at 58.

The manner in which a very appreciable saving in fin stock metal is etfected by the above-described shearing operation is schematically illustrated in FIG. 7 which is a composite view containing two shaded diagrams, namely, Diagram 7a and Diagram 7b. In Diagram 7a, the shaded area represents the surface configuration and area of one of the strips 14 of fin stock, while the dotted line 60 in this view represents the, position of the straight uninterrupted edge of a strip 14a of fin stock of equal metal gauge and identical weight which has been fabricated by conventional punching operations involving the removal of scrap metal in the form of D-shaped disks to create the voids occasioned by the various notches 24. Since the gauge of metal in each instance is the same, the surface areas of both strips 14 and 14a will be equal. In Diagram 7b, the shaded area represents the area of the strip 14a, while the dotted line 62 represents the linear edge 40 including the ears 42 of the strip 140. It is to be noted that the two shaded areas in Diagrams 7a and 7b respectively are precisely equal in size.

From the above-described Diagrams 7a and 7b, it will be appreciated that the mean width of the strips 14 which are formed by the shearing process of the present invention is less than therneanwidth of the strips 14a which are formed by conventionalpunching operations involving the removal of disks from the sheet 20 and the discarding of such disks as scrap material. Geometrical calculations will show that for any given heat-radiating area on the opposite faces of the strips 14 and Ma respectively, a narrower strip will be obtained when the shearing process of the present invention is employed.

As a consequence, a larger number of strips 14 may be cut from a sheet 20 of predetermined area than may be efliciency of the assembled heat exchange units 19 due to.

a very material increase in the linear extent of the edge 40 considered in connection with the arcuate contour of the peripheries of the various ears 42. It is a well-known fact that the heat-radiating ability of a given shape of flat fin stock depends largely upon the linear extent of any exposed edge or edges associated with such shape. In the present instance, the provision of the various ears 42 will, in small size fin stock, effect an increase of as much as 50% and, in the largest size contemplated, it will effect an increase of not less than 30%. Therefore, according to the present invention, not only will a given poundage of fin stock metal produce a larger number of fin strips than has heretofore been possible, but each fin strip so produced will have increased heat-radiating characteristics.

Still further advantages of a functional nature such as increased strength, rigidity, etc., are inherent in connection with the use of the present strips 14 of fin stock when assembled upon the serpentine length 12 of tubing and the resultant assembly embodied in a composite heat exchange unit such as the unit 16 illustrated herein. These advantages will be set forth in detail presently after the nature of the unit and its end plate structure has been made clear.-

Referring again to FIGS. 1 to 6, inclusive, the end plates or mounting brackets 16 and 18 by means of which the unit It) may be secured in position in various installations are similar in construction but differ slightly in certain respects. The end plate 16 is in the form of a relatively heavy gauge aluminum stamping which is generally of channel shape in transverse cross section and includes a pair of channel sides or flanges "70 and 72, respectively, and a connecting channel web 74. The web '74 is formed with a plurality of openings 76 therethrough (FIG. 3), such openings being formed by the provision of outstruck flanges 78 on the web. The flanges '78 are spaced from the channel side 72 and the reverse bends or bight portions 28 of the serpentine length 12 of tubing project through the openings 76 and are straddled by the flanges 78 and the channel side 72 and are frictionally confined between these spaced apart members. The opposite end regions of the channel Web 74 are provided with laterally turned attachment ears Sti having bolt holes 82 therethrough for attachment purposes, the attachment ears 8% lying in a plane which is parallel to the general plane of the serpentine tubing 12 so that the unit It as a whole may be screwed, bolted or otherwise fastened to a planar supporting surface so as to assume a position in close proximity thereto. V

, The end plate or mounting bracket ltiis also of channel shape in transverse cross section and includes channel sides or flanges 20 and 92, respectively, and a channel web 94. The channel web 94 is formed with openings 26 e are frictionally held betweenthe flanges 9S and the channel 8 side 92. The opposite end regions of the channel web 94 are provided with lateral attachment ears 160 having holes M2 therethrough, the ears 100 serving the same purpose as the ears associated with the attachment bracket 16.

Referring now to FIG. 4, it will be noted that the channel sides 70 and 96 are coplanar and these two parts constitute, in effect, seating flanges or foot portions which are adapted to seat against a supporting surface and be held thereagainst under the influence of fastening screws 194 which extend through the holes 102. The various ears 42 which, as previously stated, are in the form of major circle sectors, have their crest portions terminating in the common plane of the channel sides 70 and so that when these sides are positioned flush against a supporting surface, the crests of the ears also bear against such supporting surface and lend an appreciable degree of rigidity to the assembled and installed structure. Although the transverse width of the main body portion of each strip 14 of fin stock is less than the overall width of the unit 10 as a whole, each individual ear 42 serves, in effect, as a small supporting foot and the combined effect of all of the ears is such that when the unit is in position on a supporting surface, the same will be rigidly braced against lateral bending or crushing forces.

It is sometimes desirable that the various reach portions of a length of serpentine tube stock extend through the fin stock at a region which is substantially midway between the lateral edges of the strips instead of traversing the strips in the edge regions thereof. In such an instance, it is possible to substantially center the plane of the serpentine length 12 of tube stock. To permit such centering of the tube stock, the structure shown in FIG. 8 has been devised. The assembly of tube and fin stock shown in FIG. 8 is similar to the assembly previously described and to avoid needless repetition of description, similar reference numerals but of a higher order have been applied to the parts in FIG. 8 which correspond to similar parts in FIG. 6, for example. The forming dies by means of which the various strips 214 are severed from a single large sheet of metal stock are such that the various notches 224 are of greater depth than are the notches 24. Each notch has a wide tapering mouth portion 225 which merges with an arcuate portion 227 representing a major circle sector. The depth of the notch 224 is such that the center of the arcuate portion 227 lies substantially on the longitudinal center line midway between the longitudinal edges 222 and 240. Since the metal removed from each strip 214 to produce the notches 224 remains intact on the next succeeding strip, the configuration of the various tabs 242 corresponds to the configuration of the outline of the notches 224. The fin and tube stock assembly fragmentarily shown in FIG. 8 may be assembled in a unit similar to the unit 10, including end plates and other instrumentalities such as have previously been described in connection with. the form of the invention shown in FIGS. 1 to 6, inclusive. As in the'previously described form of the invention, the various ears 242, when considered in combination with the body portions of the strips 214, will permit the strips to be made narrower than conventional strips of fin stock having the same surface area. Since the ears 242 are of greater surface area than are the ears 42 for a given heat radiating capacity, the saving in scrap metal is appreciably greater than in the case of the form of invention previously described. Considering conventional heat exchange units, in the small size thereof, the saving in metal may be as high as 25%. Similarly, due to the very great increase in the linear edge 240, including the ears 242, the heat radiating capacity of units which embody the strips 214 may be commensurate with a 100% increase in the length of such edge. 7

Referring now to FIG. 9 wherein another slightly modified form of tube and fin stock assembly has been illustrated, again to avoid needless repetition of description, similar reference numerals of a still higher order have been applied to corresponding parts in the various views. In this form of the invention, the ears 342, instead of remaining coplanar with the body portion of the fin stock strips 314, have been bent laterally and caused to contact and overlap one another. By such an arrangement, extreme rigidity of structure will result. If desired, selected ears 342 may be provided with holes 343 therethrough for reception therethrough of anchoring screws 345.

In FIG. 10, yet another slightly modified form of fin and tube stock has been illustratd. Similar reference characters of a still higher order which have been applied to corresponding parts in the various views will again avoid detailed description. In this form of the invention, selected strips of fin stock, such as the strip 415, are made wider than the strips 414 by the height of one of the ears 442, and the ears 41? associated therewith are turned laterally and provided with holes 443 therethrough for reception of anchoring screws 4-45. Otherwise, the structure involved remains substantially the same as that shown in FlGS. 1 to 6, inclusive.

In any of the forms of the invention described above, increased rigidity may be afforded to the structure by the provision of intermediate strips of fin stock such as have been shown in FIG. 1 at 156. These latter strips may, if desired, be formed of slightly heavier gauge sheet metal and they may be devoid of heat radiating ears. Instead, the edge 152 thereof remote from the edge which contains the notches may be perfectly straight and continuous. This latter edge 152 lies in the common plane which is tangent to the crests of the various ears 42. When the unit 10 is positioned against a flat supporting surface as previously described, these edges 152 of the various strips 150 will make line contact with the supporting surface and thus lend increased rigidity to the unit 10 as a whole.

In the environment selected for illustration herein, the heat exchange unit 10 has been shown as applied to a supporting surface with the channel sides '76 and 9d (FIG. 4) positioned against the supporting surface so that the straight sides or edges 40 of the various strips 14 of fin stock face'and oppose such supporting surface. Accordingly, for purposes of description herein, both in the specification and in the appended claims, these edges 4t? of the strips 14 may be regarded as being inside edges While the edges 22 of the strips 14 may be regarded as outside edges. It will be understood, however, that the environment for the units illustrated and described herein is purely exemplary and other environments are contemplated. For example, the unit lit may be positioned against a supporting surface with the edges 22 opposing such surface, in which case the serpentine tubing 12 will assume a position of close proximity to the supporting surface instead of being spaced outwardly therefrom as shown in FIG. 6, for example. Stated otherwise, for purposes of description and claim terminology only, the general plane of the serpentine tubing 12 may be regarded as lying close to the outside face of the heat exchange unit It? while the various ears 42 may be regarded as being disposed adjacent the inside face of the unit. By reversing the positions of the two end plates or mounting brackets 16 and 18, a reversal of the position of the operative heat exchange instrumentalities relative to any given supporting surface may be elfected.

It should also be understood that although the heat exchange unit 10 illustrated herein has been shown as having an environment wherein the various ears 42 are in edge contact with the supporting surface, the installation may be such that these cars are free. in other words, the medial regions of the unit may be positioned remote from the supporting surface for free circulation of air through the various spaced fins transversely of the unit. Irrespective, however, of the particular installation with which the unit 1% may be associated, the essential features of the invention are at all times preserved.

There has been illustrated and described herein several practical embodiments of the invention, proven efiicient in actual practice. No further attempts have been made herein to illustrate other modifications and adaptations which are contemplated. It is believed, however, that the disclosures made herein will enable those skilled in the art to embody or adapt the invention in whatsoever environments may suggest themselves. The invention, therefore, is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. Only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

This application is a continuation of my patent application Serial No. 6,782, filed on February 4, 1960, and now abandoned, and entitled Heat Exchange Units.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

l. A heat exchange unit comprising, in combination, a plurality of straight, parallel, spaced apart lengths of elongated tube stock disposed in a common plane, and a series of closely spaced, elongated, parallel strips stamped frorncomparatively fiat fin stock and secured to and extending between said lengths transversely thereof, each strip presenting oppositely facing inside and outside edges respectively, one edge of each strip being formed with a series of inwardly extending notches within which the lengths of tube stock are pressed with a tight frictional fit, the other edge of each strip being formed with a series of spaced, outwardly projecting, ears thereon of a size and shape conforming precisely to the size and shape of said inwardly extending notches, each car being in transverse alignment with a respective notch and all of said ears having their outer ends terminating in a common plane, the inner regions of each notch presenting an arcuate contour which is in the form of a major circle sector.

2. A heat exchange unit comprising, incombination, a length of tube stock of serpentine configuration and presenting straight, parallel, reach sections connected together at their ends by reverse bends, and a series of closely spaced, elongated, parallel strips stamped from comparatively fiat fin stock and secured to and extending between said reach sections transversely thereof, each strip presenting oppositely facing, parallel, straight inside edges and outside longitudinal edges respectively, one longitudinal edge of each strip being formed with a series of inwardly extending notches within which the reach sections of the lengths of serpentine tube stock are pressed with a tight frictional fit, the other longitudinal edge of each strip being formed with a series of spaced, outwardly projecting, ears thereon of a size and shape conforming precisely to the size and shape of said inwardly extending notches, each ear being in transverse alignment with a respective notch and all of said ears having their outer ends terminating in a common plane, the inner region of each notch presenting an arcuate contour which is in the form of a major circle sector.

3. As a new article of manufacture, a heat exchange unit comprising a plurality of straight parallel spaced apart lengths of tube stock disposed in a common plane, and a series of closely spaced elongated parallel strips stamped from comparatively thin flat fin stock and secured to and extending transversely between said lengths, each strip having an inside longitudinal marginal region presenting a straight full length longitudinal inside edge, and also having an outside longitudinal marginal region presenting a straight full length longitudinal edge in parallel relation with the straight longitudinal inside edge of said inside longitudinal marginal region, one longitudinal marginal region of each strip being formed with a series of spaced apart notches which intersect and extend inwardly from the associated staright longitudinal edge'and within which the lengths of tube stock are respectively pressed 9 with a tight frictional fit, the straight marginal edge of the other longitudinal marginal region of each strip having formed thereon a series of spaced apart outwardly projecting cars which lie in the plane of the strip, correspond in number to the inwardly extending notches and are of a size and shape conforming precisely to the size and shape of said notches, each ear being in transverse alignment with a respective notch and all of said ears having their outer end portions terminating in a common plane, each notch being in the shape of a major circle sector and having its flat side facing and intersecting the adjacent straight longitudinal edge.

4. A heat exchange unit comprising, in combination, a length of tube stock of serpentine configuration and presenting straight, parallel, reach sections connected together 7 at their ends by reverse bends, a series of closely spaced, elongated, parallel strips of flat metal fin stock secured to and extending between said reach sections transversely thereof, each strip presenting oppositely facing inside and outside longitudinal edges respectively, one longitudinal edge of each strip being formed with a series of spaced circular notches which are in the form of major circle sectors and within which notches the reach sections of the lengths of serpentine tube stock are pressed with a tight fit, the other longitudinal edge of each strip being formed with a series of spaced, outwardly projecting, ears thereon of a size and configuration of said inwardly extending notches, said series of strips of fin stock terminating short of the reverse bends at each end of the length of tube stock, and an end plate for each end of the unit, each end plate being formed with a series of openings therethrough and through which openings the reverse bends of the tube stock extend and in which they frictionally fit, and a lateral seating flange on each end plate, said seating flangse being coplanar, each ear being in transverse alignment with a respectivenotched and all of said ears having their outer ends terminating in the common plane of said lateral seating flanges.

5. A heat exchange unit as set forth in claim 4 and wherein certain of said strips of fin stock are of heavier metal gauge than the metal gauge of the remainder thereof, the outside edges of said certain strips of fin stock being continuously straight and devoid of each with the edges of all of said certain strips of fin stock lying in the common plane of said seating flanges.

References Cited by the Examiner UNITED STATES PATENTS 2,023,739 12/35 Mason -182 XR 2,092,170 9/37 Kritzer et a1 165-151 XR 2,532,301 12/50 Hayward 165-151 XR 2,540,339 2/51 Kritzer 165182 XR FOREIGN PATENTS 839,373 8/39 France.

CHARLES SUKALO, Primary Examiner. 

1. A HEAT EXCHANGE UNIT COMPRISING, IN COMBINATION, A PLURALITY OF STRAIGHT, PARALLEL, SPACED APART LENGTHS OF ELONGATED TUBE STOCK DISPOSED IN A COMMON PLANE, AND A SERIES OF CLOSELY SPACED, ELONGATED, PARALLEL STRIPS STAMPED FROM COMPARATIVELY FLAT FIN STOCK AND SECURED TO AND EXTENDING BETWEEN SAID LENGTHS TRANSVERSELY THEREOF, EACH STRIP PRESENTING OPPOSITELY FACING INSIDE AND OUTSIDE EDGES RESPECTIVELY, ONE EDGE OF EACH STRIP BEING FORMED WITH A SERIES OF INWARDLY EXTENDING NOTCHES WITHIN WHICH THE LENGTHS OF TUBE STOCK ARE PRESSED WITH A TIGHT FRICTIONAL FIT, THE OTHER EDGE OF EACH STRIP BEING FORMED WITH A SERIES OF SPACED, OUTWARDLY PROJECTING, EARS THEREON OF A SIZE AND SHAPE CONFORMING PRECISELY TO THE SIZE AND SHAPE OF SAID INWARDLY EXTENDING NOTCHES, EACH EAR BEING IN TRANSVERSE ALIGNMENT WITH A RESPECTIVE NOTCH AND ALL OF SAID EARS HAVING THEIR OUTER ENDS TERMINATING IN A COMMON PLANE, THE INNER REGIONS OF EACH NOTCH PRESENTING AN ARCUATE CONTOUR WHICH IS IN THE FORM OF A MAJOR CIRCLE SECTOR. 